1. Field of the Invention
This invention relates to an apparatus for holding the anal sphincter in a substantially continually contracted condition and more particularly to an apparatus for applying an electrical signal to the anal sphincter to stimulate the anal sphincter such that it is maintained in a substantially contracted position.
2. Description of the Prior Art
Devices have been developed for applying an electrical signal to the anal sphincter in order to contract this muscle and hold it in a substantially contracted condition. One such device is disclosed in U.S. Pat. No. 3,650,275. In devices of this type, a square wave signal at a frequency between 18 and 90 Hz is applied to the anal sphincter. Each cycle of the square wave signal consists of a positive pulse portion followed by a negative pulse portion wherein the amplitude of the positive and negative portions are the same. The square wave signal does not have a zero output portion but rather instantaneously passes through zero when switching from the positive to negative portion. The signal applied to the anal sphincter, however, has a number of disadvantages. At a given constant current, pain or discomfort is a result of the frequency of the signal. It has been found that frequencies below 100 Hz may cause great discomfort. The signal applied to the anal sphincter by this device has a further disadvantage in that it provides no period for relaxation of the anal sphincter. Since the wave shape of the output is a square wave, it is either positive or negative at all times and has no period of zero output. The anal sphincter is thus constantly being stimulated with either the positive or negative portion of the signal and there is no time for the muscle to relax. Thus a signal of this type may cause great fatigue to the anal sphincter.
One of the problems resulting from anal muscle weakness, that is, the inability of the anal sphincter to maintain a substantially contracted condition, is that it is not possible to give patients having this problem a barium enema examination. As is readily apparent, in order to give a barium enema examination, the patient's anal sphincter must be capable of contracting and holding itself in the substantially contracted condition in order to keep the contrast fluid in the rectum and colon. No successful techniques have been developed in the prior art for giving barium enema examinations to patients suffering from anal incontinence.